feat: support line number checking in link fragment (e.g: '#L50')

Fixes #6

.eslintrc.json

@@ -1,7 +1,11 @@
 {
   "extends": ["conventions", "prettier"],
-  "plugins": ["prettier"],
+  "plugins": ["prettier", "import", "unicorn"],
+  "parserOptions": {
+    "project": "./tsconfig.json"
+  },
   "rules": {
-    "prettier/prettier": "error"
+    "prettier/prettier": "error",
+    "import/extensions": ["error", "always"]
   }
 }

.github/workflows/lint.yml

@@ -26,3 +26,4 @@ jobs:
       - run: "npm run lint:markdown"
       - run: "npm run lint:eslint"
       - run: "npm run lint:prettier"
+      - run: "npm run lint:javascript"

.husky/commit-msg

@@ -1,4 +1,3 @@
-#!/bin/sh
+#!/usr/bin/env sh
-. "$(dirname "$0")/_/husky.sh"
 
 npm run lint:commit -- --edit

.husky/pre-commit

@@ -1,5 +1,5 @@
-#!/bin/sh
+#!/usr/bin/env sh
-. "$(dirname "$0")/_/husky.sh"
 
 npm run lint:staged
+npm run lint:javascript
 npm run test

.lintstagedrc.json

@@ -1,6 +1,7 @@
 {
-  "*": ["editorconfig-checker"],
+  "**/*": ["editorconfig-checker", "prettier --write --ignore-unknown"],
-  "*.{js,jsx,ts,tsx}": ["prettier --write", "eslint --fix"],
+  "**/*.md": ["markdownlint-cli2 --fix --no-globs"],
-  "*.{json,jsonc,yml,yaml}": ["prettier --write"],
+  "**/*.{js,jsx,ts,tsx}": [
-  "*.{md,mdx}": ["prettier --write", "markdownlint-cli2 --fix"]
+    "eslint --fix --max-warnings 0 --report-unused-disable-directives"
+  ]
 }

.markdownlint-cli2.jsonc

@@ -1,11 +1,11 @@
 {
   "config": {
     "extends": "markdownlint/style/prettier",
-    "relative-links": true,
     "default": true,
-    "MD033": false
+    "relative-links": true,
+    "no-inline-html": false,
   },
-  "globs": ["**/*.{md,mdx}"],
+  "globs": ["**/*.md"],
-  "ignores": ["**/node_modules", "**/test/fixtures"],
+  "ignores": ["**/node_modules", "**/test/fixtures/**"],
-  "customRules": ["./src/index.js"]
+  "customRules": ["./src/index.js"],
 }

LICENSE

@@ -1,6 +1,6 @@
 # MIT License
 
-Copyright (c) Théo LUDWIG
+Copyright (c) Théo LUDWIG <contact@theoludwig.fr>
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -10,7 +10,7 @@
   <a href="./CODE_OF_CONDUCT.md"><img src="https://img.shields.io/badge/Contributor%20Covenant-v2.0%20adopted-ff69b4.svg" alt="Contributor Covenant" /></a>
   <br />
   <a href="https://github.com/theoludwig/markdownlint-rule-relative-links/actions/workflows/lint.yml"><img src="https://github.com/theoludwig/markdownlint-rule-relative-links/actions/workflows/lint.yml/badge.svg?branch=develop" alt="Lint" /></a>
-  <a href="https://github.com/theoludwig/markdownlint-rule-relative-linksactions/workflows/test.yml"><img src="https://github.com/theoludwig/markdownlint-rule-relative-links/actions/workflows/test.yml/badge.svg?branch=develop" alt="Test" /></a>
+  <a href="https://github.com/theoludwig/markdownlint-rule-relative-links/actions/workflows/test.yml"><img src="https://github.com/theoludwig/markdownlint-rule-relative-links/actions/workflows/test.yml/badge.svg?branch=develop" alt="Test" /></a>
   <br />
   <a href="https://conventionalcommits.org"><img src="https://img.shields.io/badge/Conventional%20Commits-1.0.0-yellow.svg" alt="Conventional Commits" /></a>
   <a href="https://github.com/semantic-release/semantic-release"><img src="https://img.shields.io/badge/%20%20%F0%9F%93%A6%F0%9F%9A%80-semantic--release-e10079.svg" alt="semantic-release" /></a>
@@ -43,9 +43,21 @@ With `awesome.md` content:
 Running [markdownlint-cli2](https://github.com/DavidAnson/markdownlint-cli2) with `markdownlint-rule-relative-links` will output:
 
 ```sh
-awesome.md:3 relative-links Relative links should be valid [Link "./invalid.txt" should exist in the file system]
+awesome.md:3 relative-links Relative links should be valid ["./invalid.txt" should exist in the file system]
 ```
 
+### Additional features
+
+- Support images (e.g: `![Image](./image.png)`).
+- Support links fragments similar to the [built-in `markdownlint` rule - MD051](https://github.com/DavidAnson/markdownlint/blob/main/doc/md051.md) (e.g: `[Link](./awesome.md#heading)`).
+- Ignore external links and absolute paths as it only checks relative links (e.g: `https://example.com/` or `/absolute/path.png`).
+
+### Limitations
+
+- Only images and links defined using markdown syntax are validated, html syntax is ignored (e.g: `<a href="./link.txt" />` or `<img src="./image.png" />`).
+
+Contributions are welcome to improve the rule, and to alleviate these limitations. See [CONTRIBUTING.md](./CONTRIBUTING.md) for more information.
+
 ### Related links
 
 - [DavidAnson/markdownlint#253](https://github.com/DavidAnson/markdownlint/issues/253)
@@ -54,7 +66,7 @@ awesome.md:3 relative-links Relative links should be valid [Link "./invalid.txt"
 
 ## Prerequisites
 
-- [Node.js](https://nodejs.org/) >= 16.0.0
+[Node.js](https://nodejs.org/) >= 16.0.0
 
 ## Installation
 
@@ -76,7 +88,7 @@ We recommend configuring [markdownlint-cli2](https://github.com/DavidAnson/markd
     "default": true,
     "relative-links": true
   },
-  "globs": ["**/*.{md,mdx}"],
+  "globs": ["**/*.md"],
   "ignores": ["**/node_modules"],
   "customRules": ["markdownlint-rule-relative-links"]
 }

jsconfig.json

@@ -0,0 +1,25 @@
+{
+  "compilerOptions": {
+    "lib": ["ESNext"],
+    "target": "ESNext",
+    "module": "CommonJS",
+    "moduleResolution": "Node",
+    "checkJs": true,
+    "allowJs": true,
+    "noEmit": true,
+    "rootDir": ".",
+    "baseUrl": ".",
+    "skipLibCheck": true,
+    "strict": true,
+    "allowUnusedLabels": false,
+    "allowUnreachableCode": false,
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitAny": true,
+    "noImplicitOverride": true,
+    "noImplicitReturns": true,
+    "noUncheckedIndexedAccess": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "forceConsistentCasingInFileNames": true,
+  },
+}

package.json

@@ -35,10 +35,11 @@
     "lint:markdown": "markdownlint-cli2",
     "lint:eslint": "eslint . --max-warnings 0 --report-unused-disable-directives --ignore-path .gitignore",
     "lint:prettier": "prettier . --check --ignore-path .gitignore",
+    "lint:javascript": "tsc --project jsconfig.json --noEmit",
     "lint:staged": "lint-staged",
-    "test": "node --test ./test",
+    "test": "node --test",
     "release": "semantic-release",
-    "postinstall": "husky install",
+    "postinstall": "husky",
     "prepublishOnly": "pinst --disable",
     "postpublish": "pinst --enable"
   },
@@ -46,23 +47,25 @@
     "markdown-it": "14.0.0"
   },
   "devDependencies": {
-    "@commitlint/cli": "18.4.3",
+    "@commitlint/cli": "18.6.0",
-    "@commitlint/config-conventional": "18.4.3",
+    "@commitlint/config-conventional": "18.6.0",
-    "@types/node": "20.10.5",
+    "@types/markdown-it": "13.0.7",
+    "@types/node": "20.11.10",
     "editorconfig-checker": "5.1.2",
     "eslint": "8.56.0",
     "eslint-config-conventions": "13.1.0",
     "eslint-config-prettier": "9.1.0",
     "eslint-plugin-import": "2.29.1",
-    "eslint-plugin-prettier": "5.1.2",
+    "eslint-plugin-prettier": "5.1.3",
     "eslint-plugin-promise": "6.1.1",
     "eslint-plugin-unicorn": "50.0.1",
-    "husky": "8.0.3",
+    "husky": "9.0.7",
     "lint-staged": "15.2.0",
-    "markdownlint": "0.32.1",
+    "markdownlint": "0.33.0",
-    "markdownlint-cli2": "0.11.0",
+    "markdownlint-cli2": "0.12.1",
     "pinst": "3.0.0",
-    "prettier": "3.1.1",
+    "prettier": "3.2.4",
-    "semantic-release": "22.0.12"
+    "semantic-release": "23.0.0",
+    "typescript": "5.3.3"
   }
 }

src/index.js

@@ -3,24 +3,33 @@
 const { pathToFileURL } = require("node:url")
 const fs = require("node:fs")
 
+const { filterTokens } = require("./markdownlint-rule-helpers/helpers.js")
 const {
-  filterTokens,
-  addError,
   convertHeadingToHTMLFragment,
   getMarkdownHeadings,
+  getMarkdownIdOrAnchorNameFragments,
+  isValidIntegerString,
+  getNumberOfLines,
+  getLineNumberStringFromFragment,
 } = require("./utils.js")
 
+/** @typedef {import('markdownlint').Rule} MarkdownLintRule */
+
+/**
+ * @type {MarkdownLintRule}
+ */
 const customRule = {
   names: ["relative-links"],
   description: "Relative links should be valid",
   tags: ["links"],
   function: (params, onError) => {
     filterTokens(params, "inline", (token) => {
-      for (const child of token.children) {
+      const children = token.children ?? []
-        const { lineNumber, type, attrs } = child
+      for (const child of children) {
+        const { type, attrs, lineNumber } = child
 
-        /** @type {string | null} */
+        /** @type {string | undefined} */
-        let hrefSrc = null
+        let hrefSrc
 
         if (type === "link_open") {
           for (const attr of attrs) {
@@ -40,30 +49,70 @@ const customRule = {
           }
         }
 
-        if (hrefSrc != null) {
+        if (hrefSrc == null) {
-          const url = new URL(hrefSrc, pathToFileURL(params.name))
+          continue
-          const isRelative =
+        }
-            url.protocol === "file:" && !hrefSrc.startsWith("/")
+
-          if (isRelative) {
+        const url = new URL(hrefSrc, pathToFileURL(params.name))
-            const detail = `Link "${hrefSrc}"`
+        const isRelative =
-
+          url.protocol === "file:" &&
-            if (!fs.existsSync(url)) {
+          !hrefSrc.startsWith("/") &&
-              addError(
+          !hrefSrc.startsWith("#")
-                onError,
+
-                lineNumber,
+        if (!isRelative) {
-                `${detail} should exist in the file system`,
+          continue
-              )
+        }
+
+        const detail = `"${hrefSrc}"`
+
+        if (!fs.existsSync(url)) {
+          onError({
+            lineNumber,
+            detail: `${detail} should exist in the file system`,
+          })
+          continue
+        }
+
+        if (url.hash.length <= 0) {
+          if (hrefSrc.includes("#")) {
+            if (type === "image") {
+              onError({
+                lineNumber,
+                detail: `${detail} should not have a fragment identifier as it is an image`,
+              })
+              continue
+            }
+
+            onError({
+              lineNumber,
+              detail: `${detail} should have a valid fragment identifier`,
+            })
+            continue
+          }
+          continue
+        }
+
+        if (type === "image") {
+          onError({
+            lineNumber,
+            detail: `${detail} should not have a fragment identifier as it is an image`,
+          })
+          continue
+        }
+
+        if (!url.pathname.endsWith(".md")) {
           continue
         }
 
-            if (type === "link_open" && url.hash !== "") {
         const fileContent = fs.readFileSync(url, { encoding: "utf8" })
         const headings = getMarkdownHeadings(fileContent)
+        const idOrAnchorNameHTMLFragments =
+          getMarkdownIdOrAnchorNameFragments(fileContent)
 
         /** @type {Map<string, number>} */
         const fragments = new Map()
 
-              const headingsHTMLFragments = headings.map((heading) => {
+        const fragmentsHTML = headings.map((heading) => {
           const fragment = convertHeadingToHTMLFragment(heading)
           const count = fragments.get(fragment) ?? 0
           fragments.set(fragment, count + 1)
@@ -73,15 +122,42 @@ const customRule = {
           return fragment
         })
 
-              if (!headingsHTMLFragments.includes(url.hash)) {
+        fragmentsHTML.push(...idOrAnchorNameHTMLFragments)
-                addError(
+
-                  onError,
+        if (!fragmentsHTML.includes(url.hash.toLowerCase())) {
-                  lineNumber,
+          if (url.hash.startsWith("#L")) {
-                  `${detail} should have a valid fragment`,
+            const lineNumberFragmentString = getLineNumberStringFromFragment(
+              url.hash,
             )
+
+            const hasOnlyDigits = isValidIntegerString(lineNumberFragmentString)
+            if (!hasOnlyDigits) {
+              onError({
+                lineNumber,
+                detail: `${detail} should have a valid fragment identifier`,
+              })
+              continue
+            }
+
+            const lineNumberFragment = Number.parseInt(
+              lineNumberFragmentString,
+              10,
+            )
+            const numberOfLines = getNumberOfLines(fileContent)
+            if (lineNumberFragment > numberOfLines) {
+              onError({
+                lineNumber,
+                detail: `${detail} should have a valid fragment identifier, ${detail} should have at least ${lineNumberFragment} lines to be valid`,
+              })
+              continue
             }
           }
-          }
+
+          onError({
+            lineNumber,
+            detail: `${detail} should have a valid fragment identifier`,
+          })
+          continue
         }
       }
     })

src/markdownlint-rule-helpers/helpers.js

@@ -0,0 +1,38 @@
+/**
+ * Dependency Vendoring of `markdownlint-rule-helpers`
+ * @see https://www.npmjs.com/package/markdownlint-rule-helpers
+ */
+
+/** @typedef {import('markdownlint').RuleParams} MarkdownLintRuleParams */
+/** @typedef {import('markdownlint').MarkdownItToken} MarkdownItToken */
+
+/**
+ * Calls the provided function for each matching token.
+ *
+ * @param {MarkdownLintRuleParams} params RuleParams instance.
+ * @param {string} type Token type identifier.
+ * @param {(token: MarkdownItToken) => void} handler Callback function.
+ * @returns {void}
+ */
+const filterTokens = (params, type, handler) => {
+  for (const token of params.tokens) {
+    if (token.type === type) {
+      handler(token)
+    }
+  }
+}
+
+/**
+ * Gets a Regular Expression for matching the specified HTML attribute.
+ *
+ * @param {string} name HTML attribute name.
+ * @returns {RegExp} Regular Expression for matching.
+ */
+const getHtmlAttributeRe = (name) => {
+  return new RegExp(`\\s${name}\\s*=\\s*['"]?([^'"\\s>]*)`, "iu")
+}
+
+module.exports = {
+  filterTokens,
+  getHtmlAttributeRe,
+}

src/utils.js

@@ -1,41 +1,8 @@
 const MarkdownIt = require("markdown-it")
 
-/**
+const { getHtmlAttributeRe } = require("./markdownlint-rule-helpers/helpers.js")
- * Calls the provided function for each matching token.
- *
- * @param {object} params RuleParams instance.
- * @param {string} type Token type identifier.
- * @param {Function} handler Callback function.
- * @returns {void}
- */
-const filterTokens = (params, type, handler) => {
-  for (const token of params.tokens) {
-    if (token.type === type) {
-      handler(token)
-    }
-  }
-}
 
-/**
+const markdownIt = new MarkdownIt({ html: true })
- * Adds a generic error object via the onError callback.
- *
- * @param {object} onError RuleOnError instance.
- * @param {number} lineNumber Line number.
- * @param {string} [detail] Error details.
- * @param {string} [context] Error context.
- * @param {number[]} [range] Column and length of error.
- * @param {object} [fixInfo] RuleOnErrorFixInfo instance.
- * @returns {void}
- */
-const addError = (onError, lineNumber, detail, context, range, fixInfo) => {
-  onError({
-    lineNumber,
-    detail,
-    context,
-    range,
-    fixInfo,
-  })
-}
 
 /**
  * Converts a Markdown heading into an HTML fragment according to the rules
@@ -72,7 +39,6 @@ const ignoredTokens = new Set(["heading_open", "heading_close"])
  * @returns {string[]}
  */
 const getMarkdownHeadings = (content) => {
-  const markdownIt = new MarkdownIt({ html: true })
   const tokens = markdownIt.parse(content, {})
 
   /** @type {string[]} */
@@ -98,8 +64,10 @@ const getMarkdownHeadings = (content) => {
       continue
     }
 
+    const children = token.children ?? []
+
     headings.push(
-      `${token.children
+      `${children
         .map((token) => {
           return token.content
         })
@@ -110,9 +78,83 @@ const getMarkdownHeadings = (content) => {
   return headings
 }
 
+const nameHTMLAttributeRegex = getHtmlAttributeRe("name")
+const idHTMLAttributeRegex = getHtmlAttributeRe("id")
+
+/**
+ * Gets the id or anchor name fragments from a Markdown string.
+ * @param {string} content
+ * @returns {string[]}
+ */
+const getMarkdownIdOrAnchorNameFragments = (content) => {
+  const tokens = markdownIt.parse(content, {})
+
+  /** @type {string[]} */
+  const result = []
+
+  for (const token of tokens) {
+    const regexMatch =
+      idHTMLAttributeRegex.exec(token.content) ||
+      nameHTMLAttributeRegex.exec(token.content)
+    if (regexMatch == null) {
+      continue
+    }
+
+    const idOrName = regexMatch[1]
+    if (idOrName == null || idOrName.length <= 0) {
+      continue
+    }
+
+    const htmlFragment = "#" + idOrName
+    if (!result.includes(htmlFragment)) {
+      result.push(htmlFragment)
+    }
+  }
+
+  return result
+}
+
+/**
+ * Checks if a string is a valid integer.
+ *
+ * Using `Number.parseInt` combined with `Number.isNaN` will not be sufficient enough because `Number.parseInt("1abc", 10)` will return `1` (a valid number) instead of `NaN`.
+ *
+ * @param {string} value
+ * @returns {boolean}
+ * @example isValidIntegerString("1") // true
+ * @example isValidIntegerString("45") // true
+ * @example isValidIntegerString("1abc") // false
+ * @example isValidIntegerString("1.0") // false
+ */
+const isValidIntegerString = (value) => {
+  const regex = /^\d+$/
+  return regex.test(value)
+}
+
+/**
+ * Gets the number of lines in a string, based on the number of `\n` characters.
+ * @param {string} content
+ * @returns {number}
+ */
+const getNumberOfLines = (content) => {
+  return content.split("\n").length
+}
+
+/**
+ * Gets the line number string from a fragment.
+ * @param {string} fragment
+ * @returns {string}
+ * @example getLineNumberStringFromFragment("#L50") // 50
+ */
+const getLineNumberStringFromFragment = (fragment) => {
+  return fragment.slice(2)
+}
+
 module.exports = {
-  filterTokens,
-  addError,
   convertHeadingToHTMLFragment,
   getMarkdownHeadings,
+  getMarkdownIdOrAnchorNameFragments,
+  isValidIntegerString,
+  getNumberOfLines,
+  getLineNumberStringFromFragment,
 }

test/basic.test.js

@@ -1,46 +0,0 @@
-const test = require("node:test")
-const assert = require("node:assert/strict")
-
-const { markdownlint } = require("markdownlint").promises
-
-const relativeLinks = require("../src/index.js")
-
-test("ensure the rule validate correctly", async () => {
-  const lintResults = await markdownlint({
-    files: ["test/fixtures/Valid.md", "test/fixtures/Invalid.md"],
-    config: {
-      default: false,
-      "relative-links": true,
-    },
-    customRules: [relativeLinks],
-  })
-  assert.equal(lintResults["test/fixtures/Valid.md"].length, 0)
-  assert.equal(lintResults["test/fixtures/Invalid.md"].length, 3)
-
-  assert.equal(
-    lintResults["test/fixtures/Invalid.md"][0]?.ruleDescription,
-    "Relative links should be valid",
-  )
-  assert.equal(
-    lintResults["test/fixtures/Invalid.md"][0]?.errorDetail,
-    'Link "./basic.test.js" should exist in the file system',
-  )
-
-  assert.equal(
-    lintResults["test/fixtures/Invalid.md"][1]?.ruleDescription,
-    "Relative links should be valid",
-  )
-  assert.equal(
-    lintResults["test/fixtures/Invalid.md"][1]?.errorDetail,
-    'Link "../image.png" should exist in the file system',
-  )
-
-  assert.equal(
-    lintResults["test/fixtures/Invalid.md"][2]?.ruleDescription,
-    "Relative links should be valid",
-  )
-  assert.equal(
-    lintResults["test/fixtures/Invalid.md"][2]?.errorDetail,
-    'Link "./Valid.md#not-existing-heading" should have a valid fragment',
-  )
-})

test/fixtures/Invalid.md

@@ -1,19 +0,0 @@
-# Invalid
-
-[basic.js](./basic.test.js)
-
-![Image](../image.png)
-
-[Link fragment](./Valid.md#not-existing-heading)
-
-## Existing Heading
-
-### Repeated Heading
-
-Text
-
-### Repeated Heading
-
-Text
-
-### Repeated Heading

test/fixtures/Valid.md

@@ -1,21 +0,0 @@
-# Valid
-
-[basic.js](../basic.test.js)
-
-![Image](./image.png)
-
-![Absolute Path](/absolute/path.png)
-
-[External https link](https://example.com/)
-
-[External https link 2](https:./external.https)
-
-[External ftp link](ftp:./external.ftp)
-
-[Link fragment](./Invalid.md#existing-heading)
-
-[Link fragment Repeated 0](./Invalid.md#repeated-heading)
-
-[Link fragment Repeated 1](./Invalid.md#repeated-heading-1)
-
-[Link fragment Repeated 2](./Invalid.md#repeated-heading-2)

test/fixtures/invalid/empty-id-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+<div id>Content</div>

test/fixtures/invalid/empty-id-fragment/empty-id-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment](./awesome.md#)

test/fixtures/invalid/ignore-empty-fragment-checking-for-image.md

@@ -0,0 +1,3 @@
+# Invalid
+
+![Image](../image.png#)

test/fixtures/invalid/ignore-fragment-checking-for-image.md

@@ -0,0 +1,3 @@
+# Invalid
+
+![Image](../image.png#non-existing-fragment)

test/fixtures/invalid/ignore-name-fragment-if-not-an-anchor/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+<input name="name-should-be-ignored" id="id-after-name" />

test/fixtures/invalid/ignore-name-fragment-if-not-an-anchor/ignore-name-fragment-if-not-an-anchor.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Invalid](./awesome.md#name-should-be-ignored)

test/fixtures/invalid/ignore-not-an-id-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+<div data-id="not-an-id-should-be-ignored">Content</div>

test/fixtures/invalid/ignore-not-an-id-fragment/ignore-not-an-id-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Invalid](./awesome.md#not-an-id-should-be-ignored)

test/fixtures/invalid/invalid-heading-with-L-fragment/awesome.md

@@ -0,0 +1 @@
+# Awesome

test/fixtures/invalid/invalid-heading-with-L-fragment/invalid-heading-with-L-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment line number 7](./awesome.md#L7abc)

test/fixtures/invalid/invalid-line-number-fragment/awesome.md

@@ -0,0 +1 @@
+# Awesome

test/fixtures/invalid/invalid-line-number-fragment/invalid-line-number-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment line number 7](./awesome.md#L7)

test/fixtures/invalid/non-existing-anchor-name-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+<a name="existing-heading-anchor">Link</a>

test/fixtures/invalid/non-existing-anchor-name-fragment/non-existing-anchor-name-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment](./awesome.md#non-existing-anchor-name-fragment)

test/fixtures/invalid/non-existing-element-id-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+<div id="existing-element-id-fragment">Content</div>

test/fixtures/invalid/non-existing-element-id-fragment/non-existing-element-id-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment](./awesome.md#non-existing-element-id-fragment)

test/fixtures/invalid/non-existing-file.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[File](./index.test.js)

test/fixtures/invalid/non-existing-heading-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+## Existing Heading

test/fixtures/invalid/non-existing-heading-fragment/non-existing-heading-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment](./awesome.md#non-existing-heading)

test/fixtures/invalid/non-existing-image.md

@@ -0,0 +1,3 @@
+# Invalid
+
+![Image](./image.png)

test/fixtures/valid/existing-anchor-name-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+<a name="existing-heading-anchor">Link</a>

test/fixtures/valid/existing-anchor-name-fragment/existing-anchor-name-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment](./awesome.md#existing-heading-anchor)

test/fixtures/valid/existing-element-id-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+<div id="existing-element-id-fragment">Content</div>

test/fixtures/valid/existing-element-id-fragment/existing-element-id-fragment.md

@@ -0,0 +1,3 @@
+# Invalid
+
+[Link fragment](./awesome.md#existing-element-id-fragment)

test/fixtures/valid/existing-file.md

@@ -0,0 +1,3 @@
+# Valid
+
+[File](../../index.test.js)

test/fixtures/valid/existing-heading-case-insensitive/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+## Existing Heading

test/fixtures/valid/existing-heading-case-insensitive/existing-heading-case-insensitive.md

@@ -0,0 +1,3 @@
+# Valid
+
+[Link fragment](./awesome.md#ExistIng-Heading)

test/fixtures/valid/existing-heading-fragment/awesome.md

@@ -0,0 +1,13 @@
+# Awesome
+
+## Existing Heading
+
+### Repeated Heading
+
+Text
+
+### Repeated Heading
+
+Text
+
+### Repeated Heading

test/fixtures/valid/existing-heading-fragment/existing-heading-fragment.md

@@ -0,0 +1,9 @@
+# Valid
+
+[Link fragment](./awesome.md#existing-heading)
+
+[Link fragment Repeated 0](./awesome.md#repeated-heading)
+
+[Link fragment Repeated 1](./awesome.md#repeated-heading-1)
+
+[Link fragment Repeated 2](./awesome.md#repeated-heading-2)

test/fixtures/valid/existing-image.md

@@ -0,0 +1,3 @@
+# Valid
+
+![Image](../image.png)

test/fixtures/valid/ignore-absolute-paths.md

@@ -0,0 +1,3 @@
+# Valid
+
+![Absolute Path](/absolute/path.png)

test/fixtures/valid/ignore-external-links.md

@@ -0,0 +1,7 @@
+# Valid
+
+[External https link](https://example.com/)
+
+[External https link 2](https:./external.https)
+
+[External ftp link](ftp:./external.ftp)

test/fixtures/valid/ignore-fragment-checking-in-own-file.md

@@ -0,0 +1,5 @@
+# Valid
+
+<div id="existing-element-id-fragment">Content</div>
+
+[Link fragment](#non-existing-element-id-fragment)

test/fixtures/valid/only-parse-markdown-files-for-fragments/awesome.html

@@ -0,0 +1,9 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>Awesome</title>
+  </head>
+  <body></body>
+</html>

test/fixtures/valid/only-parse-markdown-files-for-fragments/only-parse-markdown-files-for-fragments.md

@@ -0,0 +1,7 @@
+# Valid
+
+[Link fragment HTML](./awesome.html#existing-heading)
+
+[Link fragment TXT](./abc.txt#existing-heading)
+
+[Link fragment Image](../../image.png#existing-heading)

test/fixtures/valid/valid-heading-like-number-fragment/awesome.md

@@ -0,0 +1,3 @@
+# Awesome
+
+## L7

test/fixtures/valid/valid-heading-like-number-fragment/valid-heading-like-number-fragment.md

@@ -0,0 +1,3 @@
+# Valid
+
+[Link fragment](./awesome.md#L7)

test/fixtures/valid/valid-line-number-fragment/awesome.md

@@ -0,0 +1,9 @@
+# Awesome
+
+ABC
+
+Line 5
+
+Line 7 Text
+
+## L7

test/fixtures/valid/valid-line-number-fragment/valid-line-number-fragment.md

@@ -0,0 +1,3 @@
+# Valid
+
+[Link fragment line number 7](./awesome.md#L7)

test/index.test.js

@@ -0,0 +1,189 @@
+const { test } = require("node:test")
+const assert = require("node:assert/strict")
+
+const { markdownlint } = require("markdownlint").promises
+
+const relativeLinksRule = require("../src/index.js")
+
+/**
+ *
+ * @param {string} fixtureFile
+ * @returns
+ */
+const validateMarkdownLint = async (fixtureFile) => {
+  const lintResults = await markdownlint({
+    files: [fixtureFile],
+    config: {
+      default: false,
+      "relative-links": true,
+    },
+    customRules: [relativeLinksRule],
+  })
+  return lintResults[fixtureFile]
+}
+
+test("ensure the rule validates correctly", async (t) => {
+  await t.test("should be invalid", async (t) => {
+    const testCases = [
+      {
+        name: "with an empty id fragment",
+        fixturePath:
+          "test/fixtures/invalid/empty-id-fragment/empty-id-fragment.md",
+        error: '"./awesome.md#" should have a valid fragment identifier',
+      },
+      {
+        name: "with a name fragment other than for an anchor",
+        fixturePath:
+          "test/fixtures/invalid/ignore-name-fragment-if-not-an-anchor/ignore-name-fragment-if-not-an-anchor.md",
+        error:
+          '"./awesome.md#name-should-be-ignored" should have a valid fragment identifier',
+      },
+      {
+        name: "with a non-existing id fragment (data-id !== id)",
+        fixturePath:
+          "test/fixtures/invalid/ignore-not-an-id-fragment/ignore-not-an-id-fragment.md",
+        error:
+          '"./awesome.md#not-an-id-should-be-ignored" should have a valid fragment identifier',
+      },
+      {
+        name: "with invalid heading with #L fragment",
+        fixturePath:
+          "test/fixtures/invalid/invalid-heading-with-L-fragment/invalid-heading-with-L-fragment.md",
+        error: '"./awesome.md#L7abc" should have a valid fragment identifier',
+      },
+      {
+        name: "with a invalid line number fragment",
+        fixturePath:
+          "test/fixtures/invalid/invalid-line-number-fragment/invalid-line-number-fragment.md",
+        error:
+          '"./awesome.md#L7" should have a valid fragment identifier, "./awesome.md#L7" should have at least 7 lines to be valid',
+      },
+      {
+        name: "with a non-existing anchor name fragment",
+        fixturePath:
+          "test/fixtures/invalid/non-existing-anchor-name-fragment/non-existing-anchor-name-fragment.md",
+        error:
+          '"./awesome.md#non-existing-anchor-name-fragment" should have a valid fragment identifier',
+      },
+      {
+        name: "with a non-existing element id fragment",
+        fixturePath:
+          "test/fixtures/invalid/non-existing-element-id-fragment/non-existing-element-id-fragment.md",
+        error:
+          '"./awesome.md#non-existing-element-id-fragment" should have a valid fragment identifier',
+      },
+      {
+        name: "with a non-existing heading fragment",
+        fixturePath:
+          "test/fixtures/invalid/non-existing-heading-fragment/non-existing-heading-fragment.md",
+        error:
+          '"./awesome.md#non-existing-heading" should have a valid fragment identifier',
+      },
+      {
+        name: "with a link to an image with a empty fragment",
+        fixturePath:
+          "test/fixtures/invalid/ignore-empty-fragment-checking-for-image.md",
+        error:
+          '"../image.png#" should not have a fragment identifier as it is an image',
+      },
+      {
+        name: "with a link to an image with a fragment",
+        fixturePath:
+          "test/fixtures/invalid/ignore-fragment-checking-for-image.md",
+        error:
+          '"../image.png#non-existing-fragment" should not have a fragment identifier as it is an image',
+      },
+      {
+        name: "with a non-existing file",
+        fixturePath: "test/fixtures/invalid/non-existing-file.md",
+        error: '"./index.test.js" should exist in the file system',
+      },
+      {
+        name: "with a non-existing image",
+        fixturePath: "test/fixtures/invalid/non-existing-image.md",
+        error: '"./image.png" should exist in the file system',
+      },
+    ]
+
+    for (const { name, fixturePath, error } of testCases) {
+      await t.test(name, async () => {
+        const lintResults = await validateMarkdownLint(fixturePath)
+        assert.equal(lintResults?.length, 1)
+        assert.deepEqual(lintResults?.[0]?.ruleNames, relativeLinksRule.names)
+        assert.equal(
+          lintResults?.[0]?.ruleDescription,
+          relativeLinksRule.description,
+        )
+        assert.equal(lintResults?.[0]?.errorDetail, error)
+      })
+    }
+  })
+
+  await t.test("should be valid", async (t) => {
+    const testCases = [
+      {
+        name: "with an existing anchor name fragment",
+        fixturePath:
+          "test/fixtures/valid/existing-anchor-name-fragment/existing-anchor-name-fragment.md",
+      },
+      {
+        name: "with an existing element id fragment",
+        fixturePath:
+          "test/fixtures/valid/existing-element-id-fragment/existing-element-id-fragment.md",
+      },
+      {
+        name: "with an existing heading fragment (case insensitive)",
+        fixturePath:
+          "test/fixtures/valid/existing-heading-case-insensitive/existing-heading-case-insensitive.md",
+      },
+      {
+        name: "with an existing heading fragment",
+        fixturePath:
+          "test/fixtures/valid/existing-heading-fragment/existing-heading-fragment.md",
+      },
+      {
+        name: "should only parse markdown files for fragments checking",
+        fixturePath:
+          "test/fixtures/valid/only-parse-markdown-files-for-fragments/only-parse-markdown-files-for-fragments.md",
+      },
+      {
+        name: 'with valid heading "like" line number fragment',
+        fixturePath:
+          "test/fixtures/valid/valid-heading-like-number-fragment/valid-heading-like-number-fragment.md",
+      },
+      {
+        name: "with valid line number fragment",
+        fixturePath:
+          "test/fixtures/valid/valid-line-number-fragment/valid-line-number-fragment.md",
+      },
+      {
+        name: "with an existing file",
+        fixturePath: "test/fixtures/valid/existing-file.md",
+      },
+      {
+        name: "with an existing image",
+        fixturePath: "test/fixtures/valid/existing-image.md",
+      },
+      {
+        name: "should ignore absolute paths",
+        fixturePath: "test/fixtures/valid/ignore-absolute-paths.md",
+      },
+      {
+        name: "should ignore external links",
+        fixturePath: "test/fixtures/valid/ignore-external-links.md",
+      },
+      {
+        name: "should ignore checking fragment in own file",
+        fixturePath:
+          "test/fixtures/valid/ignore-fragment-checking-in-own-file.md",
+      },
+    ]
+
+    for (const { name, fixturePath } of testCases) {
+      await t.test(name, async () => {
+        const lintResults = await validateMarkdownLint(fixturePath)
+        assert.equal(lintResults?.length, 0)
+      })
+    }
+  })
+})

test/utils.test.js

@@ -1,9 +1,13 @@
-const test = require("node:test")
+const { test } = require("node:test")
 const assert = require("node:assert/strict")
 
 const {
   convertHeadingToHTMLFragment,
   getMarkdownHeadings,
+  getMarkdownIdOrAnchorNameFragments,
+  isValidIntegerString,
+  getNumberOfLines,
+  getLineNumberStringFromFragment,
 } = require("../src/utils.js")
 
 test("utils", async (t) => {
@@ -34,4 +38,42 @@ test("utils", async (t) => {
       ["Hello", "World", "Hello, world!"],
     )
   })
+
+  await t.test("getMarkdownIdOrAnchorNameFragments", async () => {
+    assert.deepStrictEqual(
+      getMarkdownIdOrAnchorNameFragments(
+        '<a name="anchorName" id="anchorId">Link</a>',
+      ),
+      ["#anchorId"],
+    )
+    assert.deepStrictEqual(
+      getMarkdownIdOrAnchorNameFragments('<a name="anchorName">Link</a>'),
+      ["#anchorName"],
+    )
+    assert.deepStrictEqual(
+      getMarkdownIdOrAnchorNameFragments("<a>Link</a>"),
+      [],
+    )
+    assert.deepStrictEqual(getMarkdownIdOrAnchorNameFragments("<a>"), [])
+    assert.deepStrictEqual(getMarkdownIdOrAnchorNameFragments("<a id=>"), [])
+  })
+
+  await t.test("isValidIntegerString", async () => {
+    assert.strictEqual(isValidIntegerString("1"), true)
+    assert.strictEqual(isValidIntegerString("45"), true)
+    assert.strictEqual(isValidIntegerString("1abc"), false)
+    assert.strictEqual(isValidIntegerString("1.0"), false)
+  })
+
+  await t.test("getNumberOfLines", async () => {
+    assert.strictEqual(getNumberOfLines(""), 1)
+    assert.strictEqual(getNumberOfLines("Hello"), 1)
+    assert.strictEqual(getNumberOfLines("Hello\nWorld"), 2)
+    assert.strictEqual(getNumberOfLines("Hello\nWorld\n"), 3)
+    assert.strictEqual(getNumberOfLines("Hello\nWorld\n\n"), 4)
+  })
+
+  await t.test("getLineNumberStringFromFragment", async () => {
+    assert.strictEqual(getLineNumberStringFromFragment("#L50"), "50")
+  })
 })